JP2007332450A - Hot-dipped wire, and cooling device therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hot-dipped wire having excellent appearance and capable of ensuring the workability and the corrosion resistance of the hot-dipped wire, and to provide a cooling device for manufacturing the hot-dipped wire. <P>SOLUTION: The hot-dipped wire is characterized in that the mean grain size of surface solidified crystal grains of a hot-dipped layer having the coating weight of ≥ 250 g/m<SP>2</SP>is 10-200 μm. In the hot-dipped wire cooling device, water-cooling nozzles are provided in a cooling cylinder around the hot-dipped wire so as to obtain the hot-dipped wire, and gas blowing nozzles capable of varying the ejection angle are arranged below the nozzles, and a mechanism capable of directly performing the water cooling of the surface of the hot-dipped wire is provided. The hot-dipped wire cooling device has a mechanism in which the position of the water-cooling nozzles is slidable in the moving direction of the hot-dipped wire so as to start the cooling of the hot-dipped wire in a temperature range between the solidification temperature and the solidification temperature -70°C. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a hot-dip plated wire and a cooling device for producing hot-plated wire having a plating composition mainly composed of zinc, good workability and surface properties, and less uneven thickness.

Conventionally, hot dip plating has been applied as a corrosion protection treatment for steel due to the sacrificial corrosion protection and barrier effect of zinc. When the hot-dip plated wire subjected to hot-dip plating is used for a wire mesh or the like, or when used for other fixing purposes, the plated wire is subjected to various bending processes. Since tensile strain is generated in the bent portion, cracks may occur on the plating surface (plating layer) of the hot-dip wire. When a crack occurs in the plating layer, there is a problem that a corrosion product is generated in a short time and the anticorrosion effect is lowered as compared with the case where there is no crack.
Further, when the surface of the plated wire is not smooth, there is a problem that corrosion is promoted by an increase in specific surface area as well as a reduction in commercial value due to poor appearance.
Further, even when the uneven thickness due to the uneven thickness of the plating layer is large, there is a problem that the corrosion resistance of the portion where the plating layer is thin is reduced, and this portion determines the corrosion resistance of the entire plated wire and the corrosion resistance is reduced.

  Therefore, the plating layer does not crack or peel off during the processing of various products on the hot-dip wire, the plating surface has a smooth and clean appearance, and has a uniform plating thickness to suppress the occurrence of local corrosion. It is required to be formed.

  Conventionally, as a technique for improving the workability of the plating layer, there is a technique (Patent Document 1) in which the initial crystal width of the plating layer is limited to 3 μm or less. Since it is generated from a low grain boundary, a sufficient improvement effect cannot be obtained only by reducing the primary crystal width.

  Moreover, there are various proposals as a cooling method and apparatus for manufacturing a plated wire, and a method of cooling by blowing gas and mist (Patent Document 2). There have been proposed devices and methods (Patent Documents 3, 4, and 5) for cooling by cooling air by controlling the gas flow using air or gas whose properties are controlled. However, sufficient cooling efficiency cannot be obtained by gas cooling or mist spraying. On the other hand, a method has been proposed in which a water tank is provided in order to perform more efficient water cooling, and the inside of the water tank is cooled by passing a plating wire (Patent Documents 6, 7, and 8). However, the water-cooling method using a water tank cannot prevent water leakage from the incoming portion of the plated wire, and is difficult to apply practically.

Therefore, even these prior arts are insufficient to obtain a sufficient cooling effect in thick plating with a plating adhesion amount of 250 g / m ² or more, and to obtain a plated wire with good workability, corrosion resistance and surface properties. It is.

JP 2002-235159 A JP-A-4-183844 JP 2003-193214 A Japanese Patent Laid-Open No. 10-60615 JP 2000-45056 A JP-A-6-81107 JP-A-8-60330 Japanese Utility Model Publication No.57-13880

  In view of the above, an object of the present invention is to provide a plated wire having a good appearance and a cooling device for producing the plated wire while ensuring the workability and corrosion resistance of the plated wire.

  In order to achieve the above object, the present inventors have examined in detail the solidification form and surface properties for suppressing plating cracking during hot dip wire processing, and water cooling conditions for preventing the occurrence of uneven thickness, It has been found that workability, appearance, and uneven thickness of plating thickness can be improved by performing appropriate and sufficient cooling corresponding to the wire diameter and production speed of the hot-dip wire and controlling the solidification of the hot-dip coating layer. is there.

Specifically, the solidified crystal grains were determined based on the crystal orientation analysis of the plated layer of the hot dipped wire, and the average particle diameter and cracking of the plated layer were analyzed. As a result, the surface of the plated layer was observed rather than the microstructure of the plated layer. It was revealed that the required solidified crystal grains during solidification greatly affect the occurrence of cracks. In addition, in order to obtain this appropriate solidified structure, a cooling device for ensuring sufficient and efficient cooling capacity even at a high wiring speed for obtaining a coating weight of 250 g / m ² or more is used. Thus, the solidification structure of the plating layer can be controlled, and it has been found that a hot-dip plated wire having workability, good appearance, and uniform plating thickness can be obtained, and the present invention has been completed.

The gist of the present invention is as follows.
(1) In a hot-dip galvanized wire having a plating adhesion amount of 250 g / m ² or more, the hot-dip galvanized wire characterized in that the average diameter of crystal grains on the plating surface is 10 μm or more and 200 μm or less in terms of equivalent circle is there.
(2) In a cooling device for a hot-dip plating wire that cools the hot-dip plating wire from the plating bath vertically while cooling it in the cooling tube, the hot-dip plating wire is cooled around the cooling tube through which the hot-plating wire can move. A plurality of water-cooling nozzles for spraying water are installed, and a gas spray nozzle for injecting a gas whose spray angle is variable in the forward direction and the plating wire movement direction is installed inside the cooling cylinder below the nozzles. Cooling system.
(3) The apparatus for cooling a hot dipped wire according to (2), wherein the plurality of water cooling nozzles are installed in a spiral shape so that the cooling water flows from the plurality of water cooling nozzles do not interfere with each other.
(4) The position of the water cooling nozzle is moved in the moving direction of the plating wire so that cooling can be started within the temperature range of the equilibrium solidification temperature-70 ° C or higher, which is equal to or lower than the equilibrium solidification temperature determined from the plating composition. The apparatus for cooling a hot dipped wire according to the above (1) or (2), wherein the device has a slidable mechanism.
(5) Having a mechanism capable of adjusting the angle formed by the gas flow blown from the gas spray nozzle installed below the cooling cylinder through which the hot dipped wire penetrates and the moving direction of the hot dipped wire within a range of 10 to 70 degrees. The apparatus for cooling a hot-dip galvanized wire according to any one of the above (2) to (4).

As described above, according to the present invention, the hot-dip galvanized wire has excellent workability, has a clean appearance, and can provide a plated wire excellent in corrosion resistance.
Here, the plating layer composition of the hot dipped wire of the present invention is not particularly limited, but in addition to Zn, a component containing 5 to 15% Al and further a composition containing 0.1 to 5% Mg can be applied. It is.

The present invention is a hot-dip galvanized wire excellent in workability that does not cause cracking of the plating layer as described above even when the coating weight is 250 g / m ² or more. And by cooling with a cooling device with sufficient cooling capacity, cracking of plating layer, deterioration of surface properties, small unevenness, small workability, direction properties, clean appearance, excellent corrosion resistance It is possible to manufacture a plated wire.

Hereinafter, an embodiment of the present invention will be described together with illustrated examples.
FIG. 1 and FIG. 2 show examples of photographs taken with a scanning electron microscope (hereinafter referred to as SEM) of surfaces with different plating layer solidification conditions. The plating layer structure has an Al content of 0.2% or less, and solidified crystal grains on the surface of the plating wire can be observed by SEM.
On the other hand, in the case of a plating composition containing 5% or more of Al, since it becomes eutectic solidification, it is difficult to observe by SEM due to the difference in solidification form. It is possible to obtain crystal grains by observing with a potential diffraction pattern (hereinafter referred to as EBSP).

  FIG. 1 shows water cooling started at a solidification temperature of −30 ° C. using the cooling device (water cooling device) of the present invention. FIG. 2 shows water cooling performed at a temperature lower by 85 ° C. than the solidification temperature. Apparently, the crystal grains of the plated wire of FIG. 1 cooled under the water cooling condition of the present invention are fine. As a result of measuring the average crystal grains, FIG. 1 is coarsened to 95 μm and FIG. 2 is 250 μm. The results of observing the surface of the self-diameter-plated plated wire 8 obtained by bending each plated wire with the same curvature as the wire diameter as shown in FIG. 3 are shown in FIGS. When the solidified crystal grains of the plating layer are fine, no cracks are observed on the surface as shown in FIG. 4, but when the solidified crystal grains become coarse, as shown in FIG. Cracking occurred.

Next, the reason for limiting the solidified crystal grain size will be described.
FIG. 6 shows the frequency of occurrence of plating cracks when a plating wire having a coating adhesion amount of 420 g / m ² is manufactured under various cooling conditions and the solidified crystal grains on the surface of the plating layer and the self-diametering. When the solidified crystal grains become larger than 200 μm, cracks along the crystal grain boundaries occur and plating cracks frequently occur. Therefore, the upper limit of the solidified crystal grains was set to 200 μm. On the other hand, cracks along the grain boundaries do not occur even if the crystal grains become fine grains of 10 μm or less, but because the cooling is strengthened, the surface of the plated wire is disturbed, cracks occur in the plated layer, and uneven plating thickness is generated. Since the meat (ratio between the maximum and minimum plating thickness in the C cross section) increases and the corrosion resistance deteriorates, the solidified crystal grain of 10 μm is set as the lower limit.

Here, the average crystal grain was observed by SEM at 200 times the surface of the plated wire, 10 photographs were taken, and the number of crystal grains delimited by the crystal grain boundary was measured using an image processing device. The average area per particle was obtained, and the shape of the crystal grain was converted into a circle to obtain the following equation.
Average particle size = (average area of one crystal grain × 4 / π) ^1/2

  Next, the operation of each component of the cooling device will be described.

First, the cooling device configuration will be described.
FIG. 7 shows an example of the layout of the cooling device according to the present invention. The plating wire 1 continuously moves vertically upward through a wiping device 6 installed on the bath surface through a molten metal plating bath 5, and a cooling device 2 a is installed at the upper part of the wiping device. The cooling device 2 a includes a cooling cylinder 2. As shown in FIGS. 8A and 8B, the cooling cylinder 2 through which the plating wire 1 can penetrate is a cooling water blowing nozzle 3 provided in the cooling cylinder 2. The plated wire 1 is cooled with cooling water from Since the blown-out cooling water travels down the line and falls downward due to gravity, a gas blowing nozzle 4 is installed below the cooling nozzle in order to remove the falling water droplets.

Next, the operation of each cooling device will be described.
Water-cooling nozzles are installed around the plating wire so that they are evenly spaced, and cooling water is ejected from the nozzle 3 to cool the plating wire and ensure a sufficient cooling rate, so that the solidified crystal grains are finely controlled. Have the effect of

  A plurality of cooling water blowing nozzles are installed around the cooling cylinder through which the hot dipped wire penetrates and can move. Thus, the cooling cylinder serves as a water cooling tower. In this example, four nozzles are installed at equal intervals around the circumference of the plating wire, but the number of nozzles can be further increased or decreased depending on the required cooling capacity (for example, In addition, it is possible to install not only one stage but also a plurality of stages (for example, 2 to 5 stages) in the height direction. Also, cooling water jetted from multiple water-cooling nozzles to cool one plating wire collide with each other and contact with each other, disturbing the water flow, disturbing the plating wire surface and making it impossible to cool efficiently and uniformly. In the present invention, water cooling nozzles are spirally installed around the plating wire so that the water flows do not collide with or come into contact with each other and the cooling water flow does not interfere.

  The adjustment means and mechanism in the height direction of the water cooling nozzle are not particularly limited. For example, by fixing the fixing jig of the cooling cylinder 2 to a rod-like slide bar installed in the vertical direction with respect to the bath surface, along the slide bar The cooling cylinder with the water-cooled nozzle can be moved and fixed at the desired height.

  The gas spray nozzle 4 provided in the lower part of the water cooling part is provided to prevent the cooling water from dropping, and a certain amount of gas is blown into the cooling cylinder at regular intervals around the circumference of the plating wire and is ejected to the plating wire. It has the effect | action which prevents the fall of the cooled cooling water. By adjusting the inflow gas flow rate, the gas speed, and the inflow angle, it is possible to more effectively prevent the cooling water from falling from the inside of the cooling cylinder.

Next, the reason for limiting the gas ejection angle α will be described.
The angle α of the gas jet nozzle below the cooling cylinder is such that when the gas flow in the direction perpendicular to the plating wire becomes stronger, the plating wire vibrates due to the gas flow rate and the function of pushing the cooling water to the upper part of the cooling cylinder is reduced, and water drops fall. Become intense. For this reason, the upper limit of the angle formed by the moving direction of the plating wire and the gas jet flow is set to 70 degrees. On the other hand, if the jet angle is smaller than 10 degrees, the gas flow in the cooling cylinder flows mainly in the vicinity of the inner wall, and it becomes impossible to prevent the cooling water from dropping near the plating wire. It was. More preferably, the gas ejection angle is 20 to 60 degrees. The means, method, and mechanism for making the gas spray angle α variable are not particularly limited. For example, a method of fixing the gas spray nozzle via a ball joint type universal joint, and an angle adjustment mechanism can be provided at the left and right ends of the gas spray nozzle. It is possible to arbitrarily adjust the gas spray angle by installing a fixing jig having a ratchet.

  As a result, the gas can be effectively blown into the cooling cylinder, and the cooling water sprayed on the plating wire moves upward with the movement of the plating wire without falling, and is discharged from the open part of the atmosphere. Not recovered at the drain part.

  Although this example shows an apparatus for water-cooling for each plated wire, a similar configuration is possible even when a plurality of plated wires 1 pass through the cooling cylinder 2 as shown in FIG. In this case, in particular, as shown on the left side of FIGS. 9 (a) and 9 (b), a gas nozzle for preventing water droplets from falling from the cooling cylinder 2 is installed at the end of the cooling cylinder, and at the same time, a plurality of plating wires 1 are connected to the water cooling nozzle. It is also possible to install a wide-angle nozzle so that the cooling water is applied. The plurality of cooling cylinders can drain from the lower drain.

Next, the reason for limiting the water cooling start temperature will be described.
The water cooling start temperature is a very important point in controlling the solidification structure and surface properties of the plating layer. When water cooling with a nozzle is performed in a state where the viscosity of the plating layer surface is lower than or equal to the equilibrium solidification temperature, the surface of the plating surface becomes rough and the flow of the plating layer due to water flow occurs, resulting in deterioration of surface properties and expansion of uneven thickness. For this reason, the water cooling start temperature was limited to not more than the equilibrium solidification temperature. On the other hand, when water cooling is started at a temperature lower than 70 ° C. below the equilibrium solidification temperature, the solidification of the plating layer is almost completed, and it becomes impossible to control the solidified crystal grains and surface properties. The lower limit temperature for starting water cooling was set to the plating layer equilibrium solidification temperature of -70 ° C.
Here, the equilibrium solidification temperature is a temperature at which the solid phase starts to crystallize in the liquid phase as a stable metal phase formed when the metal of the plating layer component is held at a constant temperature.

  In the present invention, the method for obtaining the equilibrium solidification temperature from the plating composition of the plating layer is not particularly limited, but the method and plating bath for obtaining the solidification temperature from the plating layer component using thermodynamic equilibrium calculation software such as Thermo-calc. The sample can be collected from the sample, and the solidification temperature can be determined experimentally by thermal analysis.

  Further, the method for measuring the surface temperature of the plated wire is not particularly limited, but it can be determined by a method in which the surface temperature is measured by directly contacting a thermocouple, or a temperature distribution measurement by a radiation thermometer or a thermoviewer.

  As mentioned above, although embodiment of this invention was explained in full detail, it shows an example of this invention and is not limited only to description content.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but it is needless to say that the following examples are not intended to limit the present invention.

Cold rolled hot-rolled wire rods are immersed in a JIS SWRM6K grade steel wire with a wire diameter of 4 mm in a 450 ° C galvanizing bath containing 0.1% Al and plated at a wire speed of 27 m / min. It was. At this time, the angle of the gas jet nozzle of the cooling device and the water cooling start temperature at the water cooling nozzle were changed to produce a plated wire having a plating adhesion amount of 420 g / m ² .

  When the equilibrium solidification temperature of this plating bath was calculated by Thermo-Calc, it was 418.7 ° C., which was about 1 ° C. lower than 419.6 ° C. without Al addition.

  In addition, solidified crystal grains were measured by observing the surface of the manufactured plated wire with an SEM, and the plating processability was evaluated in three stages: good, good, and poor by appearance observation of the surface skin that had been self-diametered. Moreover, the C cross section of the plating wire was cut, the plating thickness in the circumferential direction was observed, and the maximum plating thickness / minimum plating thickness was determined as the thickness deviation.

Table 1 also shows the water cooling conditions and the results of property evaluation of the plated wire obtained.
As shown in Table 1, cooling is performed by the cooling device of the present invention, and in the plated wire of the solidified crystal grain size range of the present invention, the crack of the plating layer, the deterioration of the surface properties, the uneven thickness are small, and the workability and the surface properties are excellent. A plated wire was obtained.

  In Comparative Examples 9 and 10, since water cooling was started at a temperature 80 ° C. lower than the equilibrium solidification temperature, the solidified crystal grains became coarse even if the arrangement of the water cooling nozzles was increased, and plating cracks along the grain boundaries occurred due to self-diametering. It is.

  Comparative Example 11 is an example in which water cooling is started at a temperature higher than the equilibrium solidification temperature, and is an example in which the surface roughness of the plated wire is large, the uneven thickness is increased to 5 or more, and the commercial value is lowered.

  Further, when the gas nozzle angle below the cooling cylinder of Comparative Example 12 is larger than the range of the present invention, the vibration of the wire becomes large, and the production of the plated wire having a stable property is unstable, plating cracking, surface skin defect, uneven thickness This is an example of increasing. In contrast, Comparative Example 13 is a case where the angle is small. In this case, too, cooling water falls from the cooling cylinder, and oxidation of the bath surface is promoted, and stable production due to a temperature drop is impossible, resulting in quality deterioration. .

It is a drawing-substitute scanning electron micrograph of the plating wire surface showing the solidified crystal grain size of the present invention. 2 is a scanning electron micrograph in place of a drawing of the surface of a plated wire having a coarsened crystal grain size. It is drawing which shows the whole surface state of a self-diameter plating wire. It is a drawing substitution scanning electron micrograph which shows the surface of the solidified crystal grain of the plating layer which plated the plating wire of this invention self-diameter, and is fine. It is a drawing-substitute scanning electron micrograph of the surface of the plated wire in which the solidified crystal grains obtained by rolling the plated wire are coarsened. It is a figure which shows the relationship between a plating wire solidification crystal grain diameter and a plating crack incidence. It is a figure which shows the cooling device arrangement layout in the hot dipping of this invention. It is a figure which shows the single wire cooling device of this invention, (a) is a top view, (b) It is a side view. It is a figure which shows the multiple plating wire cooling device of this invention, (a) is a top view, (b) It is a side view.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Plating wire 2a Cooling device 2 Cooling cylinder 3 Water cooling nozzle 4 Gas spray nozzle 5 Molten metal 6 Wiping device 7 Sinker roll 8 Self-diameter plating wire

Claims (5)

A hot dipped wire having a plating adhesion amount of 250 g / m ² or more, wherein the average diameter of crystal grains on the plating surface is 10 μm or more and 200 μm or less in terms of equivalent circle.   In a cooling device for a hot dipped wire that cools the hot dipped wire from the plating bath vertically while cooling it in the cooling tube, cooling water is sprayed to the hot dipped wire around the cooling tube through which the hot dipped wire can move. A cooling apparatus for a hot dipped plating wire, wherein a plurality of water cooling nozzles are installed, and a gas blowing nozzle for blowing a gas whose jet angle is variable in the forward direction and the plating wire moving direction is installed inside the cooling cylinder below the nozzles .   The apparatus for cooling a hot dipped wire according to claim 2, wherein the plurality of water cooling nozzles are installed in a spiral shape so that the cooling water flow from the plurality of water cooling nozzles does not interfere.   The position of the water cooling nozzle can be slid in the plating wire movement direction so that cooling can be started within the temperature range of the equilibrium solidification temperature-70 ° C or higher, which is equal to or lower than the equilibrium solidification temperature determined from the plating composition. The apparatus for cooling a hot-dip galvanized wire according to claim 1, wherein the device has a simple mechanism. It has a mechanism capable of adjusting an angle formed by a gas flow blown from a gas spray nozzle installed below a cooling cylinder through which a hot dipped wire penetrates and a moving direction of the hot dipped wire within a range of 10 to 70 degrees. The cooling apparatus of the hot dipped wire in any one of Claims 2-4.